Studies on structural characterization and electrical properties of Cu-doped BiFeO3 thin films

Cu-doped BiFeO3 (x = 0, 0.2, 0.3 and 0.5) thin films were fabricated on Pt/Si n-type substrates by a spin coating method. The phase and structure of thin films were charact- erized by x-ray diffraction (XRD). The homogeneous surface and the film thickness (200-300 nm) of the thin films were investigated by scanning with an electron microscope (SEM). X-ray absorption spectroscopy (XAS) confirmed the presence of the Fe3+ and the mixing of Cu2+ and Cu3+ oxidation states in the thin film samples. The electrical properties were studied with an Agilent4294A impedance analyzer. The influence of Cu-doping with x = 0 to x = 0.3 on the thin films can affect the structure of the thin film with decreasing crystallite sizes (2.9 nm to 2.6 nm), which lead to decreasing grain boundary conductivity (sigma(gb)) (1.1x10(-4) S/cm to 0.2x10(-4) S/cm) and increasing grain boundary resistance (R-gb) (9.1 k Omega to 35.7 k Omega.), respectively. Interestingly, the Cu-doping at x = 0.5 with large crystallite sizes (3.4 nm) can exhibit both low R-gb (6.5 k Omega.) and high sigma gb (1.5x10(-4) S/cm).